Hi sandy_mc, thank you for the answer. How to set the preview/thumnnail? I think I have it since Windows 10 can show me the a preview, right before "oWriter->WriteDNG(m_dngHost, fstream, *m_pDngNegative.Get(), NULL, dngVersion_1_3_0_0, ccUncompressed);"

Sorry for the bad formatting, i would like to edit my question with code syntax, but i did not find it.